I only have one and can't say I know these stuffs but this is my opinion:
Potty train: give them both treats. There's no harm in reinforcing it. The new puppy will learn from the older one, making your job easier. And they can be the same schedule (even though I bet the little one will need to go more often as he is smaller)
Feeding: they should be fed separately. I heard small puppies should be kept in his crate and let out a few times a day for exercise only until he's more disciplined, so I think of can keep his food bowl in his crate?
Sleeping: crate separately for now and see how it goes. If they have no problem sleeping together then I guess it fine. But I recommend each has their own crate so they can have their own alone time if they want.
Hope it helps.
